After exposing a silver halide photographic light-sensitive material to light, the material is subjected to color development, an oxidized developing agent reacts with a coupler to form a dye, with a dye image thus being formed. In this system, a subtractive process is generally used for color reproduction, in which blue, green and red colors are reproduced by forming yellow, magenta and cyan color images which are in complementary relation thereto, respectively. In general, acrylacetamide or dibenzoylmethane type couplers are employed for forming yellow color images; pyrazolone, cyanoacetyl coumarone or indazolone type couplers are used for forming magenta color images; and phenol type couplers, for example, phenols and naphthols, are utilized for forming cyan color images.
To produce color photographs, couplers which form dyes are incorporated in a developer or in a light-sensitive photographic emulsion layer(s).
It has been strongly desired to preserve color images as they were after development for a long period of time in the field of color photographic light-sensitive materials. The most fundamental method in order to resolve this problem is to improve fastness of the coupler and the dye which is formed from the coupler and the oxidation product of the developing agent.
Various couplers for forming magenta color images are known. For example, the couplers described in U.S. Pat. No. 3,935,015 are 3-(acylaminoanilino)-5-pyrazolones represented by the general formula (M) described below and are well known: ##STR1## wherein D.sub.1 represents an aryl group or a heterocyclic group, D.sub.2 represents a straight chain, branched chain or cyclic alkyl group having from 7 to 23 carbon atoms, D.sub.3 represents a coupling-off group, and L represents a halogen atom or an alkoxy group having from 1 to 18 carbon atoms.
These couplers have the characteristics that the undesired absorption of magenta azomethine dyes obtained upon color formation using the same in the red light region is low, the cut-off of the main absorption is good at the longer wavelength side, and magenta color images having a high color density are obtained because the coupling speed is high. Furthermore, the solubility in organic solvents having a high boiling point is improved, so that, after dissolving these couplers in organic solvents, the couplers can be emulsion-dispersed in an aqueous medium in the form of fine colloidal particles and then added to emulsions.
However, these couplers have the disadvantages that the degree of yellow staining at the unexposed portion after color development processing is high, and this degree of yellow staining increases upon light irradiation. They have the further disadvantages that color fading of the magenta color images obtained upon color development using these compounds occurs to a significant degree upon irradiation with light, and the color balance required for color photography is damaged by exposure to light. These disadvantages become fatal defects for color photographic light-sensitive materials, such as color printing papers and the like. Thus, improved couplers which do not have these disadvantages have been strongly desired.